In the construction of single family and multiple family dwelling or building structures, there have been many different types of building systems either used or proposed in an attempt to provide a more efficient means of construction than the conventional on site "stick built" structure. For example, it is common to construct a structure with the use of panelized exterior walls which are prefabricated in a factory by attaching sheeting such as sheets of composite boards to parallel spaced vertical wood studs extending between a wood top plate and a wood bottom plate. The window and doorway openings are preformed within the panels by constructing a header and surrounding frame for each opening.
Such prefabricated panelized exterior walls are constructed and shipped in predetermined lengths, usually, no greater than sixteen feet and either with or without fiber glass insulation between the studs so that each wall panel may be handled and erected manually by an erection crew. Panelized wall structures have also been built with a greater length, and a crane is used at the building site to move and position each building panel which is coded for erection as a predetermined wall of a predesigned building structure. After all the exterior walls are erected and the roof system is constructed along with the framework for the interior walls, the electrical wiring is installed along with fiber glass insulation and plumbing. The inner sheeting of "dry wall" or gypsum board or paneling is then attached to the studs and joist or roof system to complete the exterior and interior walls along with the ceilings.
Building structures have also been constructed with the use of prefabricated "stressed skin" panels which may consist of plywood skins or facings bonded by adhesive to opposite sides of a wood framework including a core of vertical studs extending between top and bottom wood plates and with fiberglass or expanded foam insulation between the studs. The window and door openings are preformed within the panels by means of corresponding wood frames.
Many various types of buildings have also been either constructed or proposed for construction of foam core panels wherein rectangular panels of expanded plastics foam material, such as polystyrene or polyurethane, are sandwiched between two facings or skins of sheet material such as metal or plywood. For example, U.S. Pat. No. 3,712,004 discloses a building structure constructed of preformed panels each having an expanded plastics foam core sandwiched between two relatively thick sheets of plywood. The panels are used to construct the floor, ceiling and interior walls of the building in addition to the exterior walls. As illustrated in the patent, the abutting edges of adjacent panels are coupled together by means of a key or spline formed of wood. However, other sandwiched foam core panels with metal or plywood skins have been joined by various other forms of edge connecting means or joint systems.
In the mobile home industry, it has been determined that the floor and walls of a mobile home unit can each be constructed as a one-piece foam core panel extending the full length of the mobile home, for example, 50 to 60 feet. In the construction of such wall panels for a mobile home, the window and door openings are preframed with wood members which have the same thickness as the foam core. The foam core panels and the wood frame members are then sandwiched and pressed between an inner skin of decorative prefinished plywood or gypsum board and an outer facing or skin of exterior plywood or aluminum sheeting. The inner and outer skins are laminated to the foam core panels and the wood frame members by a suitable adhesive, and vertical grooves are formed within the foam core panels for inserting or threading the necessary electrical wiring required in the exterior walls of the mobile home.
The high insulation value of expanded plastics foam material, makes the material attractive for use in exterior walls of a dwelling or building structure, especially with the higher cost of energy for heating and air conditioning. However, the cost of prefabricating custom-made wall panels with an expanded plastics foam core sandwiched between inner and outer skins or sheeting is usually higher than conventional panelized wood stud walls. Moreover, if the foam core walls are not prewired, considerable time is required to insert electrical wiring within passages or channels formed within the foam core before the skins are attached.
It has also been found that wall panels formed with an expanded foam core laminated between rigid skins, provide somewhat of a drum effect, resulting in a higher transfer of sound through the exterior walls. In addition, it is desirable for a prefabricated foam core exterior wall panel to have a substantially standard overall wall thickness such as the 41/2 inch commonly used for stud walls with dry wall sheeting or the 51/8 inch thickness which is common for exterior stud walls with plaster interior. These standard wall thicknesses are desirable for accommodating preformed window and door jamb units.